The Boro goalkeeper's mis-hit clearance led to Frederic Kanoute's winner 14 minutes from time.

Ugo Ehiogu was dismissed for a second yellow card a minute from time.

West Ham leapfrogged Middlesbrough and into 10th place in the table in the process.

Jermain Defoe's early drive appeared destined for the net but Paul Ince's slide tackle took the pace off it and Schwarzer held on low to his right.

Boro went close when Benito Carbone swung over an 11th minute corner and strike partner Alen Boksic rose to glance a header wide.

Carbone volleyed straight at David James seconds after miscueing an attempt from a Franck Queudrue cross.

The Italian was then at the heart of a fine move as his crossfield pass released Queudrue, who in turn squared the ball across James' six-yard box but Jonathan Greening could not convert at full stretch.

That chance was followed by a volley from Noel Whelan which just cleared the bar.

West Ham, without suspended trio Paolo di Canio, Sebastian Schemmel and Trevor Sinclair, were robbed of another of their regulars shortly before the break as Don Hutchison was stretchered off after falling in an innocuous-looking tangle with Queudrue.

Vladimir Labant replaced him and was booked seconds afterwards for a trip on Ince.

After the break Boro were only denied the lead by a superb save by James after Ince had rifled his shot towards the bottom corner from 10 yards.

Just as it looked as if the game was petering towards a goalless draw, Schwarzer's gaffe put West Ham in the lead.

He raced out of his area but scuffed his clearance straight to Labant just inside the visitors' half.

Labant looked up and picked out Kanoute, 15 yards out, and the Frenchman controlled with his right and swept in a volley with his left through Queudrue's legs, with Schwarzer scrambling to get back on to his line.